U.S. patent application number 16/852679 was filed with the patent office on 2020-11-12 for image sensor with pixels including photodiodes sharing floating diffusion region.
The applicant listed for this patent is SAMSUNG ELECTRONICS CO., LTD.. Invention is credited to KYUNGHO LEE, EUNSUB SHIM.
Application Number | 20200358971 16/852679 |
Document ID | / |
Family ID | 1000004815623 |
Filed Date | 2020-11-12 |
View All Diagrams
United States Patent
Application |
20200358971 |
Kind Code |
A1 |
SHIM; EUNSUB ; et
al. |
November 12, 2020 |
IMAGE SENSOR WITH PIXELS INCLUDING PHOTODIODES SHARING FLOATING
DIFFUSION REGION
Abstract
An image sensor operating in multiple resolution modes including
a low resolution mode and a high resolution mode includes a pixel
array including a plurality of pixels, wherein each pixel in the
plurality of pixels comprises a micro-lens, a first subpixel
including a first photodiode, a second subpixel including a second
photodiode, and the first subpixel and the second subpixel are
adjacently disposed and share a floating diffusion region. The
image sensor also includes a row driver providing control signals
to the pixel array to control performing of an auto focus (AF)
function, such that performing the AF function includes performing
the AF function according to pixel units in the high resolution
mode and performing the AF function according to pixel group units
in the low resolution mode. A resolution corresponding to the low
resolution mode is equal to or less than 1/4 times a resolution
corresponding to the high resolution mode.
Inventors: |
SHIM; EUNSUB; (HWASEONG-SI,
KR) ; LEE; KYUNGHO; (SUWON-SI, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SAMSUNG ELECTRONICS CO., LTD. |
Suwon-Si |
|
KR |
|
|
Family ID: |
1000004815623 |
Appl. No.: |
16/852679 |
Filed: |
April 20, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04N 9/0455 20180801;
H04N 5/349 20130101; H04N 5/378 20130101; H04N 5/3698 20130101 |
International
Class: |
H04N 5/349 20060101
H04N005/349; H04N 9/04 20060101 H04N009/04; H04N 5/369 20060101
H04N005/369 |
Foreign Application Data
Date |
Code |
Application Number |
May 7, 2019 |
KR |
10-2019-0053242 |
Aug 16, 2019 |
KR |
10-2019-0100535 |
Claims
1. An image sensor selectively adapted for use in multiple
resolution modes including a low resolution mode and a high
resolution mode, the image sensor comprising: a pixel array
comprising a plurality of pixels, wherein each pixel in the
plurality of pixels comprises a micro-lens, a first subpixel
including a first photodiode, and a second subpixel including a
second photodiode, and the first subpixel and the second subpixel
are adjacently disposed and share a floating diffusion region; and
a row driver configured to provide control signals to the pixel
array to control performing of an auto focus (AF) function, the AF
function including performing the AF function according to pixel
units in the high resolution mode and performing the AF function
according to pixel group units in the low resolution mode, wherein
a resolution corresponding to the low resolution mode is equal to
or less than 1/4 times a resolution corresponding to the high
resolution mode.
2. The image sensor of claim 1, wherein the plurality of pixels
includes a first subpixel array and a second subpixel array, the
first subpixel array includes horizontal pixels, and the second
subpixel array includes vertical pixels.
3. The image sensor of claim 2, wherein the row driver is further
configured to provide the control signals such that at least one of
the first subpixel and the second subpixel of at least one of the
horizontal pixels in the first subpixel array performs the AF
function in the high resolution mode.
4. The image sensor of claim 3, wherein the row driver is further
configured to provide the control signals such that; photoelectric
charge generated by the first subpixels of the at least one of the
horizontal pixels is accumulated in the floating diffusion region,
then photoelectric charge in the floating diffusion region is
reset, and then photoelectric charge generated by the second
subpixels of the at least one of the horizontal pixels is
accumulated in the floating diffusion region.
5. The image sensor of claim 3, wherein the at least one of the
horizontal pixels in the first subpixel array includes not all of
the horizontal pixels in the first subpixel array.
6. The image sensor of claim 2, wherein the first sub pixel array
comprises a first horizontal pixel and a second horizontal pixel
adjacently disposed, in response to a control signal provided from
the row driver, a first floating diffusion region of the first
horizontal pixel and a second floating diffusion region of the
second horizontal pixel are electrically connected to each other,
thereby enabling the first horizontal pixel and the second
horizontal pixel to share the floating diffusion region.
7. The image sensor of claim 2, wherein the horizontal pixels
include a first horizontal pixel and a second horizontal pixel
sharing the floating diffusion region, and the row driver is
configured to provide the control signals, such that the first
subpixels of the first horizontal pixel and the second horizontal
pixel simultaneously accumulate photoelectric charge in the
floating diffusion region in the low resolution mode.
8. The image sensor of claim 2, wherein the horizontal pixels of
the first subpixel array include a first pixel group and a second
pixel group adjacently disposed to the first pixel group, the first
pixel group and the second pixel group include horizontal pixels
arranged in a first direction and a second direction, all of the
horizontal pixels of the first pixel group are associated with a
first color filter, and all of the horizontal pixels of the second
pixel group are associated with a second color filter different
from the first color filter.
9. The image sensor of claim 2, wherein the horizontal pixels of
the first subpixel array include a first pixel group and a second
pixel group adjacently disposed to the first pixel group, the first
pixel group and the second pixel group include horizontal pixels
arranged in a first direction and a second direction, at least one
of the horizontal pixels of the first pixel group is associated
with a first color filter, and at least one of the horizontal
pixels of the second pixel group is associated with a second color
filter different from the first color filter.
10. The image sensor of claim 9, wherein the first color filter and
the second color filter is respectively selected from a group of
color filters including; a red filter, a blue filter, a green
filter, a white filter and a yellow filter.
11. The image sensor of claim 2, wherein the horizontal pixels of
the first subpixel array include a first pixel group and a second
pixel group adjacently disposed to the first pixel group, the first
pixel group and the second pixel group include horizontal pixels
arranged in a first direction and a second direction, at least one
of the horizontal pixels of the first pixel group is associated
with a first color filter and at least another one of the
horizontal pixels of the first pixel group is associated with a
second color filter, and at least one of the horizontal pixels of
the second pixel group is associated with a third color filter and
at least another one of the horizontal pixels of the second pixel
group is associated with a fourth color filter.
12. The image sensor of claim 11, wherein the first color filter
and the third color filter are different color filters.
13. The image sensor of claim 12, wherein the second color filter
and the fourth color filter are the same color filter.
14. The image sensor of claim 2, wherein the horizontal pixels of
the first subpixel array include a first pixel group and a second
pixel group adjacently disposed to the first pixel group, the first
pixel group and the second pixel group include horizontal pixels
arranged in a first direction and a second direction, at least two
of the horizontal pixels of the first pixel group are respectively
associated with a first color filter and a second color filter
different from the first color filter, and at least two of the
horizontal pixels of the second pixel group are respectively
associated with a third color filter and a fourth color filter
different from the third color filter.
15. An image sensor selectively adapted for use in multiple
resolution modes including a low resolution mode, a medium
resolution mode, and a high resolution mode, the image sensor
comprising: a pixel array comprising a plurality of pixels arranged
in a row direction and a column direction, wherein each pixel in
the plurality of pixels has a shared pixel structure, wherein the
shared pixel structure comprises: a first subpixel including a
first photoelectric conversion element selectively transmitting
photoelectric charge to a floating diffusion region via a first
transmission transistor in response to a first transmission signal,
a second subpixel including a second photoelectric conversion
element selectively transmitting photoelectric charge to the
floating diffusion region via a second transmission transistor in
response to a second transmission signal, a reset transistor
configured to selectively reset photoelectric charge accumulated in
the floating diffusion region in response to a reset signal, a
driver transistor and a selection transistor selectively connecting
the floating diffusion region to a pixel signal output in response
to a selection signal, the floating diffusion region, the reset
transistor, the driver transistor and the selection transistor are
shared by the first subpixel and the second subpixel, and the first
subpixel and the second subpixel are adjacently disposed; and a row
driver configured to provide the first transmission signal, the
second transmission signal, the reset signal and the selection
signal, such that performing of an auto focus (AF) function
includes performing the AF function according to units of the
plurality of pixels in the high mode, performing the AF function
according to units of pixels arranged in the same row in one pixel
group in the medium resolution, and performing the AF function
according to units of pixel groups in low resolution mode.
16. The image sensor of claim 15, wherein a plurality of pixels
comprised in the same pixel group among the plurality of pixel
groups are configured to share a floating diffusion region, and the
row driver is configured to provide the first transmission signal,
the second transmission signal, the reset signal and the selection
signal so that photoelectric charges generated by the plurality of
pixels comprised in the same pixel group are all accumulated into
the floating diffusion region and then are reset.
17. The image sensor of claim 15, wherein at least two pixel groups
disposed adjacent to each other among are configured to share a
floating diffusion region.
18. The image sensor of claim 15, wherein the high resolution mode
has a first resolution, the medium resolution mode has second
resolution ranging from between about 1/4 the first resolution to
about 1/2 the first resolution, and the low resolution mode has a
third resolution less than or equal to about 1/4 the first
resolution.
19. An image sensor selectively adapted for use in multiple
resolution modes including a low resolution mode, a medium
resolution mode, and a high resolution mode, the image sensor
comprising: a controller configured to control the operation of a
row driver and a signal read unit; a pixel array comprising a
plurality of pixels arranged in a row direction and a column
direction and configured to provide a pixel signal in response to
received incident light, wherein each pixel in the plurality of
pixels comprises a micro-lens, a first subpixel including a first
photodiode, a second subpixel including a second photodiode, and
the first subpixel and the second subpixel are adjacently disposed
and share a floating diffusion region, wherein the row driver is
configured to provide control signals to the pixel array to control
performing of an auto focus (AF) function, such that performing of
an auto focus (AF) function includes performing the AF function
according to units of the plurality of pixels in the high mode,
performing the AF function according to units of pixels arranged in
the same row in one pixel group in the medium resolution, and
performing the AF function according to units of pixel groups in
low resolution mode.
20. The image sensor of claim 19, wherein the high resolution mode
has a first resolution, the medium resolution mode has second
resolution ranging from between about 1/4 the first resolution to
about 1/2 the first resolution, and the low resolution mode has a
third resolution less than or equal to about 1/4 the first
resolution.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Korean Patent
Application Nos. 10-2019-0053242, filed on May 7, 2019 and
10-2019-0100535, filed on Aug. 16, 2019, in the Korean Intellectual
Property Office, the collective subject matter of which is hereby
incorporated by reference.
BACKGROUND
[0002] The inventive concept relates to image sensors, and more
particularly, to image sensors including a plurality of pixels,
wherein each pixel includes a plurality of subpixels including a
photodiode.
[0003] Image sensors include a pixel array. Each pixel among the
plurality of pixels in the pixel array may include a photodiode.
Certain image sensors may perform an auto-focus (AF) function to
improve the imaging accuracy of an object.
SUMMARY
[0004] The inventive concept provides an image sensor capable of
accurately performing an auto-focus function across a range of
illumination environments.
[0005] According to one aspect of the inventive concept, there is
provided an image sensor selectively adapted for use in multiple
resolution modes including a low resolution mode and a high
resolution mode. The image sensor includes; a pixel array
comprising a plurality of pixels, wherein each pixel in the
plurality of pixels comprises a micro-lens, a first subpixel
including a first photodiode, a second subpixel including a second
photodiode, and the first subpixel and the second subpixel are
adjacently disposed and share a floating diffusion region. The
image sensor also includes a row driver configured to provide
control signals to the pixel array to control performing of an auto
focus (AF) function, such that performing the AF function includes
performing the AF function according to pixel units in the high
resolution mode and performing the AF function according to pixel
group units in the low resolution mode. a resolution corresponding
to the low resolution mode is equal to or less than 1/4 times a
resolution corresponding to the high resolution mode.
[0006] According to another aspect of the inventive concept, there
is provided an image sensor selectively adapted for use in multiple
resolution modes including a low resolution mode, a medium
resolution mode and a high resolution mode. The image sensor
includes a pixel array including a plurality of pixels arranged in
a row direction and a column direction, wherein each pixel in the
plurality of pixels has a shared pixel structure. The shared pixel
structure includes; a first subpixel including a first
photoelectric conversion element selectively transmitting
photoelectric charge to a floating diffusion region via a first
transmission transistor and in response to a first transmission
signal, a second subpixel including a second photoelectric
conversion element selectively transmitting photoelectric charge to
the floating diffusion region via a second transmission transistor
in response to a second transmission signal, a reset transistor
configured to selectively reset photoelectric charge accumulated in
the floating diffusion region in response to a reset signal, a
driver transistor and a selection transistor selectively connecting
the floating diffusion region to a pixel signal output in response
to a selection signal, the floating diffusion region, reset
transistor, driver transistor and selection transistor are shared
by the first subpixel and the second subpixel and the first
subpixel and the second subpixel are adjacently disposed. the image
sensor also includes a row driver configured to provide the first
transmission signal, the second transmission signal, the reset
signal and the selection signal, such that performing of an auto
focus (AF) function includes performing the AF function according
to units of the plurality of pixels in the high resolution mode,
performing the AF function according to units of pixels arranged in
the same row in one pixel group in the medium resolution, and
performing the AF function according to units of pixel groups in
low resolution mode.
[0007] According to another aspect of the inventive concept, there
is provided an image sensor selectively adapted for use in multiple
resolution modes including a low resolution mode, a medium
resolution mode and a high resolution mode. The image sensor
includes; a controller configured to control the operation of a row
driver and a signal read unit, and a pixel array comprising a
plurality of pixels arranged in a row direction and a column
direction and configured to provide a pixel signal in response to
received incident light, wherein each pixel in the plurality of
pixels comprises a micro-lens, a first subpixel including a first
photodiode, a second subpixel including a second photodiode, and
the first subpixel and the second subpixel are adjacently disposed
and share a floating diffusion region, wherein the row driver is
configured to provide control signals to the pixel array to control
performing of an auto focus (AF) function, such that performing of
an auto focus (AF) function includes performing the AF function
according to units of the plurality of pixels in the high
resolution mode, performing the AF function according to units of
pixels arranged in the same row in one pixel group in the medium
resolution, and performing the AF function according to units of
pixel groups in low resolution mode.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Embodiments of the inventive concept may be more clearly
understood upon consideration of the following detailed description
taken in conjunction with the accompanying drawings in which:
[0009] FIG. 1 is a block diagram illustrating a digital imaging
device according to an embodiment of the inventive concept;
[0010] FIG. 2 is a block diagram further illustrating in one
embodiment the image sensor 100 of FIG. 1;
[0011] FIGS. 3A, 3B, 4A, 4B and 4C are respective diagrams further
illustrating certain aspects of the pixel array 110 of the image
sensor 100 of FIG. 2;
[0012] FIG. 5 is a circuit diagram illustrating in one embodiment
an arrangement of first and second subpixels sharing a floating
diffusion region;
[0013] FIGS. 6A, 6B, 6C, 6D and 6E are respective diagrams further
illustrating a plurality of subpixels sharing a floating diffusion
region among the subpixels included in a first subpixel array of
FIG. 3A;
[0014] FIG. 7 is a circuit diagram illustrating in one embodiment
an arrangement of subpixels sharing a floating diffusion
region;
[0015] FIGS. 8, 9, 10 and 11 are respective timing diagrams further
illustrating in several embodiments certain timing relationships
between various control signals in the operation of the image
sensor 100 of FIG. 2; and
[0016] FIG. 12 is a diagram further illustrating in still another
embodiment the pixel array 110 of FIG. 2.
DETAILED DESCRIPTION
[0017] Figure (FIG. 1 is a block diagram illustrating a digital
imaging device 1000 according to an embodiment of the inventive
concept.
[0018] Referring to FIG. 1, the digital imaging device 1000
generally comprises an imaging unit 1100, an image sensor 100, and
a processor 1200. Here, it is assumed that the digital imaging
device 1000 is capable of performing a focus detection
function.
[0019] The overall operation of the digital imaging device 1000 may
be controlled by the processor 1200. In the illustrated embodiment
of FIG. 1, it is assumed that the processor 1200 provides certain
signals controlling various components of the digital imaging
device 1000. For example, the processor 1200 may provide a lens
driver signal applied to a lens driver 1120, an aperture driver
signal applied to an aperture driver 1140, and a controller signal
applied to a controller 120.
[0020] The imaging unit 1100 generally includes one or more
element(s) configured to receiving incident light associated with
an object 2000 being imaged by the digital imaging device. In this
regard, the object 2000 may be a single object, a collection of
objects, or a distributed field of object. Further in this regard,
the term "incident light" should be broadly construed to mean any
selected range of electro-magnetic energy across one or more bands
of the electro-magnetic spectrum (e.g., wavelengths discernable to
the human eye) capable of being imaged by the digital imaging
device 1000.
[0021] In the illustrated embodiment of FIG. 1, the imaging unit
1100 includes the lens driver 1120 and aperture driver 1140, as
well as a lens 1110 and an aperture 1130. Here, the lens 1110 may
include one or more lenses arranged singularly or in combination to
effectively capture the incident light associated with the object
2000.
[0022] In particular, the lens driver 1120 operates to control the
operation of the lens 1110 to accurately capture the incident light
associated with the object 2000. Accordingly, the lens driver 1120
is responsive to the focus detection function performed by the
digital imaging device 1000, as may be transmitted to the lens
driver 1120 by the processor 1200. In this manner, the focal
position of the lens 1110 may be controlled by one or more control
signals provided from the processor 1200.
[0023] In this regard, it should be noted that the term "control
signal" is used hereafter to denote one or more signal(s), whether
analog or digital in nature and having various formats, that are
used to adjust or control the operation of a component within the
digital imaging device 1000.
[0024] Thus, the lens driver 1120 may adjust the focal position of
the lens 1110 with respect to the movement, orientation and/or
distance of the object 2000 relative to the lens 1110 in order to
correct focal mismatches between a given focal position of the lens
1110 and the object 2000.
[0025] Within the illustrated embodiment of FIG. 1, the image
sensor 100 may be used to convert incident light received via the
imaging unit 1100 into a corresponding image signal. The image
sensor 100 may generally include a pixel array 110, the controller
120, and a signal processor 130. Here, incident light passing
through the lens 1110 and the aperture 1130 reaches an incident
light receiving surface of the pixel array 110.
[0026] The pixel array 110 may include a Complementary Metal Oxide
Semiconductor (CMOS) image sensor (CIS) capable of converting the
energy of the incident light into corresponding electrical
signal(s). In this regard, the sensitivity of the pixel array 110
may be adjusted by the controller 120. The resulting collection of
corresponding electrical signal(s) may be further processed by the
signal processor 130 to provide an image signal.
[0027] In certain embodiments of the inventive concept, the pixel
array 110 may include a plurality of pixels selectively capable of
performing an auto focus (AF) function or a distance measurement
function.
[0028] Thus, in certain embodiments of the inventive concept, the
processor 1200 may receive a first image signal and a second image
signal from the signal processor 130 and perform a phase difference
determination using the first image signal and the second image
signal. The processor 1200 may then determine an appropriate focal
position, identify a focus direction, and/or a calculate a distance
between the digital imaging device and the object 2000 on the basis
of a result of the phase difference determination. In this manner,
the processor 1200 may be used to provide the signal(s) applied to
the lens driver 1120 in order to properly adjust the focal position
of the lens 1110 based on the results of the phase difference
determination operation.
[0029] FIG. 2 is a block diagram further illustrating in one
embodiment the image sensor 100 of FIG. 1. Here, the image sensor
100 may be selectively adapted for use in various resolution modes
in response to the illumination environment associated with the
object 2000. That is, in certain embodiments of the inventive
concept, the digital imaging device of FIG. 1 may make a
determination regarding an appropriate resolution mode (e.g., low
or high) and selectively adapted (or configure) the image sensor
100 accordingly.
[0030] Referring to FIG. 2, the image sensor 100 comprises a row
driver 140 and a signal read unit 150 in addition to the pixel
array 110, the controller 120 and the signal processor 130. Here,
it is assumed that the signal read unit 150 includes a
correlated-double sampling circuit (CDS) 151, an analog-to-digital
converter (ADC) 153 and a buffer 155.
[0031] The pixel array 110 comprises a plurality of pixels. This
plurality of pixels may be variously designated for operation (or
functionally divided) into one or more subpixel arrays. For
example, the pixel array 110 may include a first subpixel array
110_1 and a second subpixel array 110_2. In certain embodiments of
the inventive concept, the first subpixel array 110_1 includes a
plurality of horizontal pixels PX_X capable of performing an AF
function in a first direction (e.g., a row direction), and the
second subpixel array 110_2 includes a plurality of vertical pixels
PX_Y capable of performing an AF function in a second direction
(e.g., a column direction). In certain embodiments of the inventive
concept each subpixel array may be further, functionally divided
into two (2) or more pixel groups.
[0032] Those skilled in the art will recognize that the terms
"horizontal" and "vertical"; "first direction" and "second
direction", as well as "row direction" and "column direction" are
relative in nature, and are used to describe various, relative
orientation relationships between recited elements and
components.
[0033] Each horizontal pixel PX_X of the first subpixel array 110_1
includes at least two (2) photodiodes adjacently disposed in the
first (or row) direction of a matrix arrangement including at least
one row. Each horizontal pixel PX_X of the first subpixel array
110_1 also includes a micro-lens ML disposed on the at least two
(2) photodiodes.
[0034] Each vertical pixels PX_Y of the second subpixel array 110_2
includes at least two (2) photodiodes adjacently disposed in the
second (or column) direction of a matrix including at least one
column. Each vertical pixel PX_Y of the second subpixel array 110_2
also includes a micro-lens ML disposed on the at least two (2)
photodiodes.
[0035] With this configuration, each of the horizontal pixel PX_X
of the first subpixel array 110_1 may perform an AF function in the
first direction, and each vertical pixel PX_Y of the second
subpixel array 110_2 may perform an AF function in the second
direction. Since each of the horizontal pixels PX_X and each of the
vertical pixels PX_Y includes at least two photodiodes as well as a
micro-lens, each one of the plurality of pixels (including both
horizontal PX_X pixels and vertical PX_Y pixels) may generate a
pixel signal capable of effectively performing an AF function. In
this manner, an image sensor according to an embodiment of the
inventive concept may readily provide an enhanced AF function.
[0036] In certain embodiments of the inventive concept, the width
of each horizontal pixel PX_X of the first subpixel array 110_1 may
range from between about 0.5 .mu.m and about 1.8 .mu.m. The width
of each vertical pixel PX_Y of the second subpixel array 110_2 may
also range from between about 0.5 .mu.m and about 1.8 .mu.m.
Alternatively, the width of the plurality of horizontal and
vertical pixels, PX_X and PX_Y, may range from between about 0.64
.mu.m and about 1.4 .mu.m.
[0037] In certain embodiments of the inventive concept, the
horizontal pixels PX_X of the first subpixel array 110_1 may be
grouped into one or more pixel groups, and the vertical pixels PX_Y
of the second subpixel array 110_2 may be grouped into one or more
pixel groups.
[0038] According to a given configuration and definition of a
plurality of pixels and pixel groups, the image sensor 100 of FIG.
2 may selectively perform an AF function according using pixels
units or according to pixel group units. For example, given the
digital imaging device 1000 of FIG. 1 is adapted for use in a high
resolution mode, the image sensor may perform an AF function
according to pixel units (i.e., in response to various pixel
signal(s) provided by individual pixels--e.g., horizontal and/or
vertical pixels). Alternately, given the digital imaging device
1000 of FIG. 1 is adapted for use in a low resolution mode, the
image sensor may perform an AF function according to pixel group
units (i.e., in response to various pixel signal(s) provided by
pixel groups).
[0039] Respective embodiments further illustrating possible
configurations for the first and second subpixel arrays 110_1 and
110_2 will be described hereafter with reference to FIGS. 3A and
3B.
[0040] Returning to FIG. 2, each pixel in the pixel array 110 may
respectively output a pixel signal (see e.g., the VOUT signal of
FIG. 5) to the CDS 151 through one of the first through n-1.sup.th
column output lines CLO_0 to CLO_n-1. Pixel signals output from the
horizontal pixels PX_X of the first subpixel array 110_1 and the
vertical pixels PX_Y of the second subpixel array 110_2 may be
phase signals used to calculate a phase difference. The phase
signals may include information associated with the positioning of
object(s) imaged by the image sensor 100. Accordingly, a focus
position for the lens 1110 (of FIG. 1) may be calculated in
response to the calculated phase difference(s). For example, a
focus position for the lens 1110 corresponding to a phase
difference of `0` may be deemed an optimal focus position. In
certain embodiments of the inventive concept, given operation in
the high resolution mode, a selected plurality of pixels (e.g.,
including both horizontal and vertical pixels, PX_X and PX_Y) may
from the pixel array 110 may be used to perform an AF function.
Indeed, in certain embodiment all of the horizontal pixels in the
first subpixel array 110_1 and all of the vertical pixels in the
second subpixel array 110_2 may collectively be used to perform the
AF function when the digital imaging device 100 is being operated
in the high resolution mode.
[0041] Additionally or alternately, the horizontal pixels PX_X of
the first subpixel array 110_1 and the vertical pixels PX_Y of the
second subpixel array 110_2 may be used to measure a distance
between the object 2000 and the digital imaging device 1000. In
order to measure a distance between the digital imaging device 100
and the object 2000, some additional information may be necessary
or convenient to use. Examples of additional information may
include: phase difference between the object 2000 and the image
sensor 100, lens size for the lens 1110, current focus position for
the lens 1110, etc.
[0042] In the embodiment illustrated in FIG. 2, the controller 120
may be used to control the row driver 140, such that the pixel
array 110 effectively captures incident light to effectively
accumulate corresponding photoelectric charge (or temporarily store
the accumulated photoelectric charge). Here, the term
"photoelectric charge" is used to denote electrical charge
generated by at least one subpixel in the pixel array in response
to incident light. The pixel array may then output an electrical
signal (i.e., a pixel signal) corresponding to the accumulated
photoelectrical charge. Additionally, the controller 120 may
control the operation of the signal read unit 150, such that the
pixel array 110 may accurately measure a level of the pixel signal
provided by the pixel array 110.
[0043] The row driver 140 may be used to generate various control
signals. Here, examples of control signals include; reset control
signals RS, transmission control signals TS, and selection signals
SELS that may be variously provided to control the operation of the
pixel array 110. Those skilled in the art will recognize that the
choice, number and definition of various control signals is a
matter of design choice.
[0044] In certain embodiments of the inventive concept, the row
driver 140 may be used determine the activation timing and/or
deactivation timing (hereafter, singularly or collectively in any
pattern, "activation/deactivation") of the reset control signals
RS, transmission control signals TS, and selection signals SELS
variously provided to the horizontal pixels PX_X of the first
subpixel array 110_1 and the vertical pixels PX_Y of the second
subpixel array 110_2, in response to various factors, such as
high/low resolution mode of operation, types of AF function being
performed, distance measurement function, etc.
[0045] The CDS 151 may sample and hold a pixel signal provided from
the pixel array 110. The CDS 151 may doubly sample a level of
certain noise and a level based on the pixel signal to output a
level corresponding to a difference therebetween. Moreover, the CDS
151 may receive a ramp signal generated by a ramp signal generator
157 and may compare the ramp signal with the pixel signal to output
a comparison result. The ADC 153 may convert an analog signal,
corresponding to the level received from the CDS 151, into a
digital signal. The buffer 155 may latch the digital signal, and
the latched digital signal may be sequentially output to the
outside of the signal processor 130 or the image sensor 100.
[0046] The signal processor 130 may perform signal processing on
the basis of the digital signal received from the buffer 155. For
example, the signal processor 130 may perform noise decrease
processing, gain adjustment, waveform standardization processing,
interpolation processing, white balance processing, gamma
processing, edge emphasis processing, etc. Moreover, the signal
processor 130 may output information, obtained through signal
processing performed in an AF operation, to the processor 1200 to
allow the processor 1200 to perform a phase difference operation
needed for the AF operation. In an embodiment, the signal processor
130 may be included in a processor (1200 of FIG. 1) provided
outside the image sensor 100.
[0047] FIGS. 3A and 3B are respective diagrams further illustrating
in certain embodiments the pixel array 110 of FIG. 2. FIG. 3A is a
diagram further illustrating in one embodiment the first subpixel
array 110_1 of the pixel array 110, and FIG. 3B is a diagram
further illustrating in another embodiment the second subpixel
array 110_2 of the pixel array 110.
[0048] Referring to FIG. 3A, the first subpixel array 110_1
includes a plurality of horizontal pixels PX_X arranged in a matrix
defined according to a row direction (i.e., a first direction X)
and a column direction (i.e., a second direction Y). Each of the
horizontal pixels PX_X in the first subpixel array 110_1 may
include a micro-lens ML.
[0049] In the illustrated example of FIG. 3A, the first subpixel
array 110_1 includes first to fourth pixel groups PG1, PG2, PG3 and
PG4, wherein the first pixel group PG1 and the second pixel group
PG2 are adjacently disposed in the first direction X, while the
third pixel group PG3 and the fourth pixel group PG4 are adjacently
disposed in the first direction X. The first pixel group PG1 and
the third pixel group PG3 are adjacently disposed in the second
direction Y, while the second pixel group PG2 and the fourth pixel
group PG4 are adjacently disposed in the second direction Y.
[0050] In the illustrated embodiment of FIG. 3A, each of the first,
second, third and fourth pixel groups PG1 to PG4 includes four (4)
horizontal pixels PX_X, but other embodiments of the inventive
concept are not limited to this configuration. For example, each of
the first, second, third and fourth pixel groups PG1 to PG4 may
include eight (8) horizontal pixels PX_X arranged in two (2) rows
and four (4) columns.
[0051] Here, however, the first pixel group PG1 includes first to
eighth subpixels SPX11 to SPX18, where first subpixel SPX11 and
second subpixel SPX12 are configured in one horizontal pixel PX_X,
third subpixel SPX13 and fourth subpixel SPX14 are configured in
another horizontal pixel PX_X, fifth subpixel SPX15 and sixth
subpixel SPX16 are configured in another horizontal pixel PX_X, and
seventh subpixel SPX17 and eighth subpixel SPX18 are configured in
still another horizontal pixel PX_X.
[0052] With analogous configurations, the second pixel group PG2
includes first to eighth subpixels SPX21 to SPX28; the third pixel
group PG3 includes first to eighth subpixels SPX31 to SPX38; and
the fourth pixel group PG4 includes first to eighth subpixels SPX41
to SPX48.
[0053] Here, it should be noted that each horizontal pixel PX_X
includes two (2) subpixels adjacently disposed to each other in the
first direction X.
[0054] The first subpixel array 110_1 may further include one or
more color filter(s), such that respective horizontal pixels,
respective collection(s) of horizontal pixels and/or respective
pixel groups may selectively sense various light wavelengths, such
as those conventionally associated with different colors of the
visible light spectrum. For example, in certain embodiments of the
inventive concept, various color filter(s) associated with the
first subpixel array 110_1 may include a red filter (R) for sensing
red, a green filter (G) for sensing green, and a blue filter (B)
for sensing blue. That is, various color filters (e.g., a first
color filter, a second color filter, etc.) may be respectively
selected from a group of color filters including; a red filter, a
blue filter, a green filter, a white filter, a yellow filter,
etc.
[0055] Here, each of the first, second, third and fourth pixel
groups PG1 to PG4 may variously associated with one or more color
filters.
[0056] In one embodiment of the inventive concept consistent with
the configuration shown in FIG. 3A, the first, second, third and
fourth pixel groups PG1 to PG4 may be disposed in the first
subpixel array 110_1 according to a Bayer pattern. That is, the
first pixel group PG1 and the fourth pixel group PG4 may associated
with a green filter (G), the second pixel group PG2 may associated
with a red filter (R), and the third pixel group PG3 may be
associated with a blue filter (B).
[0057] However, the foregoing embodiment of the first subpixel
array 110_1 is just one example of many different configurations
wherein a color filter is variously associated with one or more
pixels selected from one or more pixel groups. Additionally or
alternatively, embodiments of the inventive concept may variously
include; a white filter, a yellow filter, a cyan filter, and/or a
magenta filter.
[0058] With reference to FIG. 3A, each of the subpixels SPX11 to
SPX18, SPX21 to SPX28, SPX31 to SPX38, and SPX41 to SPX48 included
in the first subpixel array 110_1 may include a corresponding
photodiode. Thus, each of the horizontal pixels PX_X will include
at least two (2) photodiodes adjacently disposed to each other in
the first direction X. A micro-lens ML may be disposed on the at
least two (2) photodiodes.
[0059] With this exemplary configuration in mind, the amount of
photoelectric charge generated by the at least two (2) photodiodes
included in each horizontal pixel PX_X will vary with the shape
and/or refractive index of an associated micro-lens ML.
Accordingly, an AF function performed in the first direction X may
be based on a pixel signal corresponding to the amount of
photoelectric charge generated by the constituent, at least two (2)
photodiodes.
[0060] For example, an AF function may be performed by using a
pixel signal output by the first subpixel SPX11 of the first pixel
group PG1 and a pixel signal output by the second subpixel SPX12 of
the first pixel group PG1. Accordingly, an image sensor according
to an embodiment of the inventive concept may selectively perform
an AF function according to pixel units in a first operating (e.g.,
a high resolution) mode. The performance of an AF function
according to "pixel units" in a high resolution mode allows for the
selective use of one, more than one, or all of the horizontal
pixels PX_X in the first subpixel array 110_1 during the
performance of an AF function.
[0061] By way of comparison, an image sensor according to an
embodiment of the inventive concept may selectively perform an AF
function according to pixel group units in a second operating
(e.g., a low resolution) mode. The performance of an AF function
according to "pixel group units" in a low resolution mode allows
for the selective use of one, more than one, or all of the pixel
groups (e.g., PG1, PG2, PG3 and PG4) in the first subpixel array
110_1 during the performance of an AF function. For example, an AF
function may be performed by processing a first pixel signal
corresponding to the amount of photoelectric charge generated by a
photodiode of each of the first subpixel SPX11, the third subpixel
SPX13, the fifth subpixel SPX15, and the seventh subpixel SPX17 of
the first pixel group PG1 and a second pixel signal corresponding
to the amount of photoelectric charge generated by a photodiode of
each of the second subpixel SPX12, the fourth subpixel SPX14, the
sixth subpixel SPX16, and the eighth subpixel SPX18 of the first
pixel group PG1. Given this selective approach to performing an AF
function by the image sensor 100, and even in environmental
circumstances wherein a relatively low level incident light is
captured by the pixel array 110 (e.g., a level of incident light
conventional inadequate to accurately perform an AF function), an
image sensor according to an embodiment of the inventive concept
may nonetheless faithfully perform the AF function.
[0062] In this regard, those skilled in the art will recognize that
the terms "high resolution" and "low resolution" are relative terms
and may be arbitrarily defined according to design. However, in the
context of certain embodiments of the inventive concept, a first
level of image resolution associated with a low resolution mode may
be understood as being less than or equal to 1/4 of a second level
of image resolution associated with a high resolution mode.
[0063] With the foregoing in mind, other embodiments of the
inventive concept may provide digital imaging devices capable of
operating (or selectively adapted for use) in more than two
resolution modes. For example, a digital imaging device according
to certain embodiments of the inventive concept may be selectively
adapted for use in a low resolution mode and a high resolution
mode, as described above, and additionally in a medium resolution
mode. Here, for example, an image sensor according to embodiments
of the inventive concept may perform an AF function according to
pixel units by selecting a set of horizontal pixels PX_X (or a set
of vertical pixels PX_Y) included in a single pixel group (e.g.,
PG1) and arranged in a same row (or the same column).
[0064] Extending this example, an AF function may be performed by
processing a first pixel signal corresponding to an amount of
photoelectric charge generated by the photodiodes of each of the
first subpixel SPX11 and the third subpixel SPX13 of the first
pixel group PG1, and a second pixel signal corresponding to the
amount of photoelectric charge generated by a photodiode of each of
the second subpixel SPX12 and the fourth subpixel SPX14 of the
first pixel group PG1. Alternatively, an AF function may be
performed by processing a first pixel signal corresponding to an
amount of photoelectric charge generated by a photodiode of each of
the first subpixel SPX11 and the fifth subpixel SPX15 of the first
pixel group PG1 and a second pixel signal corresponding to an
amount of photoelectric charge generated by a photodiode of each of
the second subpixel SPX12 and the sixth subpixel SPX16 of the first
pixel group PG1.
[0065] Recognizing here again that the terms "high resolution",
"medium resolution", and "low resolution" are relative terms, and
may be arbitrarily defined according to design, in the context of
certain embodiments of the inventive concept, a third level of
image resolution associated with the medium resolution mode may be
understood as being greater than 1/4 of a second level of image
resolution associated with a high resolution mode, but less than
1/2 of the second level of the image resolution associated with the
high resolution mode.
[0066] Referring to FIG. 3B, the second subpixel array 110_2
includes a plurality of vertical pixels PX_Y arranged in a matrix
defined in relation to the first direction X and the second
direction Y. In certain embodiments, each of the vertical pixels
PX_Y may include a single micro-lens ML.
[0067] As shown in FIG. 3B, the second subpixel array 110_2
includes first, second, third and fourth pixel groups PG1Y to PG4Y.
However, other embodiments of the inventive concept may include
less or more pixel groups. Here, the first pixel group PG1Y
includes first to eighth subpixels SPX11Y to SPX18Y. The first
subpixel SPX11Y and the second subpixel SPX12Y are configured as
one vertical pixel PX_Y, the third subpixel SPX13Y and the fourth
subpixel SPX14Y are configured as another vertical pixel PX_Y, the
fifth subpixel SPX15Y and the sixth subpixel SPX16Y are configured
as another vertical pixel PX_Y, and the seventh subpixel SPX17Y and
the eighth subpixel SPX18Y are configured as still another vertical
pixel PX_Y. Moreover, for example, the second pixel group PG2Y may
include first to eighth subpixels SPX21Y to SPX28Y, the third pixel
group PG3Y may include first to eighth subpixels SPX31Y to SPX38Y,
and the fourth pixel group PG4Y may include first to eighth
subpixels SPX41Y to SPX48Y. That is, one pixel PX_Y may include two
subpixels disposed adjacent to each other in the second direction
Y.
[0068] The respective vertical pixels of the second subpixel array
110_2 or various collections of the respective vertical pixels of
the second subpixel array 110_2 may be variously associated with
one or more color filter(s), as described above in relation to FIG.
3A.
[0069] Thus, each of the subpixels SPX11Y to SPX18Y, SPX21Y to
SPX28Y, SPX31Y to SPX38Y, and SPX41Y to SPX48Y included in the
second subpixel array 110_2 may include one corresponding
photodiode. Therefore, each of the vertical pixels PX_Y will
include at least two (2) photodiodes adjacently disposed to each
other in the second direction Y. The amount of photoelectric charge
generated by the at least two (2) photodiodes included in a
vertical pixel PX_Y may vary with the shape and/or the refractive
index of the associated micro-lens ML. An AF function in the second
direction Y may be performed based on a pixel signal corresponding
to the amount of photoelectric charge generated by photodiodes
included in one pixel PX_Y. For example, an AF function may be
performed by using a first pixel signal output by the first
subpixel SPX11Y of the first pixel group PG1Y and a second pixel
signal output by the second subpixel SPX12Y of the first pixel
group PG1Y. Therefore, the image sensor according to an embodiment
may perform an AF function according to pixel units in the high
resolution mode.
[0070] On the other hand, an image sensor according to embodiments
of the inventive concept may perform an AF function according to
pixel groups in the low resolution mode. For example, an AF
function in the second direction Y may be performed by processing a
first pixel signal corresponding to an amount of photoelectric
charge generated by a photodiode of each of the first subpixel
SPX11Y, the third subpixel SPX13Y, the fifth subpixel SPX15Y, and
the seventh subpixel SPX17Y of the first pixel group PG1Y, and a
second pixel signal corresponding to an amount of photoelectric
charge generated by a photodiode of each of the second subpixel
SPX12Y, the fourth subpixel SPX14Y, the sixth subpixel SPX16Y, and
the eighth subpixel SPX18Y of the first pixel group PG1Y.
[0071] Analogously with the foregoing description of the embodiment
of FIG. 3A, the embodiment of FIG. 3B may be altered to operate in
a medium resolution mode, as well as the high resolution mode and
the low resolution mode.
[0072] FIGS. 4A, 4B and 4C are respective diagrams further
illustrating in various embodiments the pixel array 110 of the
image sensor 100 of FIG. 2. Here, like reference numbers and labels
are used among FIGS. 3A, 4A, 4B and 4C.
[0073] Referring to FIG. 4A, the horizontal pixels PX_X of a first
subpixel array 110_1a are variously associated with (i.e.,
functionally configured together with) different color filters; a
red filter (R), a green filter (G), a blue filter (B) and a white
(or yellow) filter (W) or (Y). Here again, first, second third, and
fourth pixel groups PG1a to PG4a are assumed for the first subpixel
array 110_1a.
[0074] In FIG. 4A, both the first pixel group PG1a and the fourth
pixel group PG4a have horizontal pixels PX_X variously associated
with a green filter (G) and a white filter (W). That is, a seventh
subpixel SPX17 and an eighth subpixel SPX18 of the first pixel
group PG1a are associated with the white filter (W), and a first
subpixel SPX41 and a second subpixel SPX42 of the fourth pixel
group PG4a are associated with the white filter (W). Alternatively,
the horizontal pixels PX_X of the first pixel group PG1a and the
fourth pixel group PG4a might be associated with the green filter
(G) and a yellow filter (Y).
[0075] Analogously, horizontal pixels PX_X of the second pixel
group PG2a are variously associated with the red filter (R) and the
white filter (W). That is, a fifth subpixel SPX25 and a sixth
subpixel SPX26 of the second pixel group PG2a are associated with
the white filter (W) or alternately the yellow filter (Y), and
horizontal pixels PX_X of the third pixel group PG3a are variously
associated with the blue filter (B) and the white filter (W). That
is, a third subpixel SPX33 and a fourth subpixel SPX34 of the third
pixel group PG3a are associated with the white filter (W) or
alternately the yellow filter (Y).
[0076] Thus, as illustrated in FIG. 4A certain embodiments of the
inventive concept may associate adjacent horizontal pixels PX_X
selected from different pixel groups with a color filter, while
non-selected horizontal pixels PX_X from each of the different
pixel groups are variously associated with different color
filters.
[0077] In contrast and as illustrated in FIG. 4B, respective pixel
groups (e.g., first to fourth pixel groups PG1b to PG4b) may be
respectively associated with one of a set of color filters. For
example, the first pixel group PG1b is associated with the green
filter (G), the second pixel group PG2b is associated with the red
filter (R), the third pixel group PG3b is associated with the blue
filter (B), and the fourth pixel group PG4b is associated with the
white filter (W) or the yellow filter (Y).
[0078] In further contrast and as illustrated in FIG. 4C, each
individual horizontal pixel PX_X may be respectively associated
with a selected one of the set of color filters, without regard to
inclusion of the individual horizontal pixel PX_X in a particular
pixel group. Thus, each one of the first to fourth pixel groups
PG1c to PG4c includes color filters having different colors.
[0079] As illustrated in FIG. 4C, the first pixel group PG1c and
the fourth pixel group PG4c include a green filter (G) and a white
filter (W) or a yellow filter (Y). The first, second, seventh, and
eighth subpixels SPX11, SPX12, SPX17, and SPX18 of the first pixel
group PG1c are associated with the white filter (W) or the yellow
filter (Y), whereas the first, second, seventh, and eighth
subpixels SPX41, SPX42, SPX47, and SPX48 of the fourth pixel group
PG4c are associated with the white filter (W) or the yellow filter
(Y). Moreover, the third, fourth, fifth, and sixth subpixels SPX13,
SPX14, SPX15, and SPX16 of the first pixel group PG1c are
associated with the green filter (G), whereas the third, fourth,
fifth, and sixth subpixels SPX43, SPX44, SPX45, and SPX46 of the
fourth pixel group PG4c are associated with the green filter
(G).
[0080] The second pixel group PG2c includes horizontal pixels PX_X
variously associated with the red filter (R) and the white filter
(W) or the yellow filter (Y). Hence, the first, second, seventh,
and eighth subpixels SPX21, SPX22, SPX27, and SPX28 of the second
pixel group PG2c are each associated with the white filter (W) or
the yellow filter (Y), whereas the third, fourth, fifth, and sixth
subpixels SPX23, SPX24, SPX25, and SPX26 of the second pixel group
PG2c are associated with the red filter (R).
[0081] The third pixel group PG3c includes horizontal pixels PX_X
variously associated with the blue filter (B) and the white filter
(W) or the yellow filter (Y). Hence, the first, second, seventh,
and eighth subpixels SPX31, SPX32, SPX37, and SPX38 of the third
pixel group PG3c are associated with the white filter (W) or the
yellow filter (Y), whereas the third, fourth, fifth, and sixth
subpixels SPX33, SPX34, SPX35, and SPX36 of the third pixel group
PG3c are each associated with the blue filter (B).
[0082] FIG. 5 is a circuit diagram illustrating an arrangement of
first and second subpixels sharing a floating diffusion region
according to certain embodiments of the inventive concept. In FIG.
5, a first subpixel and a second subpixel of a pixel (e.g., a
horizontal pixel or a vertical pixel) are configured within a
shared pixel structure to share a floating diffusion region.
However, other embodiments of the inventive concept may include
other arrangements of various subpixels sharing a floating
diffusion region.
[0083] In FIG. 5, the first subpixel includes a first photodiode
PD11, a first transmission transistor TX11, a selection transistor
SX1, a drive transistor SF1, and a reset transistor RX1. The second
subpixel includes a second photodiode PD12, a second transmission
transistor TX12, as well as the selection transistor SX1, the drive
transistor SF1, and the reset transistor RX1. With this
configuration (e.g., a shared pixel structure SHPX), the first
subpixel and the second subpixel may effectively share a floating
diffusion region FD1 as well as the selection transistor SX1, the
drive transistor SF1, and the reset transistor RX1. Those skilled
in the art will recognize that one or more of the selection
transistor SX1, the drive transistor SF1, and the reset transistor
RX1 may be omitted in other configurations.
[0084] Here, each of the first photodiode PD11 and the second
photodiode PD12 may generate photoelectric charge as a function of
received incident light. For example, each of the first photodiode
PD11 and the second photodiode PD12 may be a P-N junction diode
that generates photoelectric charge (i.e., an electron as a
negative photoelectric charge and a hole as a positive
photoelectric charge) in proportion to an amount of incident light.
That is, each of the first photodiode PD11 and the second
photodiode PD12 may include at least one photoelectric conversion
element, such as a phototransistor, a photogate, a pinned
photodiode (PPD), etc.
[0085] The first transmission transistor TX11 may be used to
transmit photoelectric charge generated by the first photodiode
PD11 to the floating diffusion region FD1 in response to a first
transmission control signal TS11 applied to the first transmission
transistor TX11. Thus, when the first transmission transistor TX11
is turned ON, photoelectric charge generated by the first
photodiode PD11 is transmitted to the floating diffusion region FD1
wherein it is accumulated (or stored) in the floating diffusion
region FD1. Likewise, when the second transmission transistor TX12
is turned ON in response to a second transmission control signal
TS12, photoelectric charge generated by the second photodiode PD12
is transmitted to, and is accumulated by, the floating diffusion
region FD1.
[0086] In this regard, the floating diffusion region FD1 operates
as a photoelectric charge capacitor. Thus, as the number of
photodiodes operationally connected to the floating diffusion
region FD1 increases in certain embodiments of the inventive
concept, capacitance storing capability of the floating diffusion
region FD1 must also increase.
[0087] The reset transistor RX1 may be used to periodically reset
the photoelectric charge accumulated in the floating diffusion
region FD1. A source electrode of the reset transistor RX may be
connected to the floating diffusion region FD1, and a drain
electrode thereof may be connected to a source voltage VPIX. When
the reset transistor RX is turned ON in response to a reset control
signal RS1, the source voltage VPIX connected to the drain
electrode of the reset transistor RX1 may be applied to the
floating diffusion region FD1. When the reset transistor RX1 is
turned ON, photoelectric charge accumulated in the floating
diffusion region FD1 may be discharged, and thus, the floating
diffusion region FD1 may be reset.
[0088] The drive transistor SF1 may be controlled based on the
amount of photoelectric charge accumulated in the floating
diffusion region FD1. The drive transistor SF1 may be a buffer
amplifier and may buffer a signal in response to the photoelectric
charge accumulated by the floating diffusion region FD1. The drive
transistor SF1 may amplify a potential varying in the floating
diffusion region FD1, and output the amplified potential as a pixel
signal VOUT to a column output line (e.g., one of the first to
n-1.sup.th column output lines CLO_0 to CLO_n-1 of FIG. 2).
[0089] A drain terminal of the selection transistor SX1 may be
connected to a source terminal of the drive transistor SF1, and in
response to a selection signal SELS1, the selection transistor SX1
may output the pixel signal VOUT to a CDS (e.g., the CDS 151 of
FIG. 2) through a corresponding column output line.
[0090] One or more of the first transmission control signal TS11,
the second transmission control signal TS12, the reset control
signal RS1, and the selection signal SELS1, as illustrated in FIG.
5, may be control signals provided by a row driver (e.g., the row
driver 140 of FIG. 2) operating in relation to a pixel array (e.g.,
pixel array 110 of FIG. 2) according to embodiments of the
inventive concept.
[0091] FIGS. 6A, 6B, 6C, 6D and 6E are respective diagrams
variously illustrating subpixel arrangements that share a floating
diffusion region. Such subpixel arrangements may be included in
subpixel arrays of pixels arrays included in embodiments of the
inventive concept (e.g., the first subpixel array 110_1 of FIG. 3A,
the second subpixel array 110_2 of FIG. 3B and the subpixel
array(s) of FIGS. 4A to 4C).
[0092] Referring to FIG. 6A, a first subpixel array 100_1e may
include first to fourth pixel groups PG1e to PG4e, and each of the
first to fourth pixel groups PG1e to PG4e may include a plurality
of horizontal pixels PX_X. Subpixels included in each of the
horizontal pixels PX_X may be configured in a shared pixel
structure SHPX1 which shares different floating diffusion regions.
That is, the shared pixel structure SHPX1 may be a 2-shared
structure including two subpixels. Hence, two subpixels will share
a single floating diffusion region.
[0093] For example, a first subpixel SPX11 and a second subpixel
SPX12 of the first pixel group PG1e may be configured in a shared
pixel structure SHPX1 which shares a first floating diffusion
region, while a third subpixel SPX13 and a fourth subpixel SPX14 of
the first pixel group PGle may be configured in a shared pixel
structure SHPX1 which shares a different floating diffusion region.
In this case, the first subpixel SPX11 and the third subpixel SPX13
are associated with different floating diffusion regions.
[0094] The foregoing description of the first pixel group PGle may
be applied to the second to fourth pixel groups PG2e to PG4e.
[0095] In the high resolution mode, the first subpixel array 100_1e
may accumulate all of the photoelectric charge generated by the
least two (2) photodiodes of different subpixels in a floating
diffusion region. For example, the first subpixel array 100_1e may
output a reset voltage as a pixel signal (e.g., VOUT of FIG. 5),
and then, may output a pixel signal VOUT based on the first
subpixel SPX11, and then may output a pixel signal VOUT based on
the first subpixel SPX11 and the second subpixel SPX12. That is,
subpixels (e.g., the first subpixel SPX11 and the second subpixel
SPX12) configuring together in a single horizontal pixel may share
a floating diffusion region (e.g., the floating diffusion region
FD1 of FIG. 5), and thus, may output a pixel signal VOUT based on a
photoelectric charge generated by a first photodiode (e.g., the
first photodiode PD11 of FIG. 5) of the first subpixel SPX11 and a
photoelectric charge generated by a second photodiode (e.g., the
second photodiode PD12 of FIG. 5) of the second subpixel SPX12.
Such a readout method may be a
reset-signal-signal-reset-signal-signal-reset-signal-signal-reset-signal--
signal (RSSRSSRSSRSS) readout method.
[0096] However, operation of an image sensor including the first
subpixel array 100_1e in the high resolution mode according to an
embodiment is not limited thereto. Although the first subpixel
SPX11 and the second subpixel SPX12 share the floating diffusion
region FD1, the first subpixel array 100_1e may output a pixel
signal VOUT based on the first subpixel SPX11, subsequently reset
the floating diffusion region FD1 to output a reset voltage as a
pixel signal VOUT, and subsequently output a pixel signal VOUT
based on the second subpixel SPX12. Such a readout method may be a
reset-signal-reset-signal-reset-signal-reset-signal-reset-signal-reset-si-
gnal-reset-signal-reset-signal (RSRSRSRSRSRSRSRS) readout
method.
[0097] Thus, image sensors consistent with embodiments of the
inventive concept may variously adjust the number of floating
diffusion region resets, in obtaining a pixel signal VOUT output
from each of subpixels included in one shared pixel structure SHPX1
sharing one floating diffusion region. As the number of floating
diffusion region resets increases, the time taken in obtaining a
pixel signal VOUT output from each of subpixels included in one
shared pixel structure SHPX1 also increases, but a floating
diffusion region having a relatively low capacitance may be formed
and a conversion gain may increase. On the other hand, as the
number of floating diffusion region resets decreases, a floating
diffusion region having a high capacitance may be needed. However,
the time taken in obtaining a pixel signal VOUT output from each of
subpixels included in one shared pixel structure SHPX1 may
decrease.
[0098] In certain embodiments of the inventive concept, the first
to fourth pixel groups PGle to PG4e of the first subpixel array
100_1e may be respectively connected to different column output
lines (e.g., respective corresponding column output lines of the
first to n-1.sup.th column output lines CLO_0 to CLO_n-1). For
example, a plurality of pixels PX_X of the first pixel group PGle
may be connected to the first column output line CLO_0, a plurality
of pixels PX_X of the second pixel group PG2e may be connected to
the second column output line CLO_1, a plurality of pixels PX_X of
the third pixel group PG3e may be connected to the third column
output line CLO_2, and a plurality of pixels PX_X of the fourth
pixel group PG4e may be connected to the fourth column output line
CLO_3.
[0099] In this case, an image sensor including the first subpixel
array 100_1e may perform an analog pixel binning operation in the
low resolution mode. That is, in the low resolution mode, the first
subpixel array 100_1e may output a reset voltage as a pixel signal
VOUT through the first column output line CLO_0, subsequently
output a pixel signal VOUT based on the first, third, fifth, and
seventh subpixels SPX11, SPX13, SPX15, and SPX17 through the first
column output line CLO_0, and subsequently output a pixel signal
VOUT based on the first to eighth subpixels SPX11 to SPX18 through
the first column output line CLO_0. Such a readout method may be a
reset-signal-signal (RSS) readout method.
[0100] Alternatively, in the low resolution mode, the first
subpixel array 100_1e may output the reset voltage as a pixel
signal VOUT through the first column output line CLO_0,
subsequently output the pixel signal VOUT based on the first,
third, fifth, and seventh subpixels SPX11, SPX13, SPX15, and SPX17
through the first column output line CLO_0, subsequently output the
reset voltage as a pixel signal VOUT through the first column
output line CLO_0 again, and subsequently output a pixel signal
VOUT based on the second, fourth, sixth, and eighth subpixels
SPX12, SPX14, SPX16, and SPX18 through the first column output line
CLO_0. Such a readout method may be a reset-signal-reset-signal
(RS-RS) readout method.
[0101] However, image sensors according to embodiments of the
inventive concept are not limited thereto, and the plurality of
horizontal pixels PX_X included in the first subpixel array 100_1e
may be respectively connected to different column output lines. In
this case, an image sensor including the first subpixel array
100_1e may perform a digital pixel binning operation in the low
resolution mode. For example, in the low resolution mode, the first
subpixel array 100_1e may output different pixel signals VOUT based
on the first, third, fifth, and seventh subpixels SPX11, SPX13,
SPX15, and SPX17 through different column output lines, and each of
the pixel signals VOUT may be converted into a digital signal by a
CDS (for example, 151 of FIG. 2) and an ADC (for example, 153 of
FIG. 2) and may be stored in a buffer (for example, 155 of FIG. 2).
The buffer 155 may output data, corresponding to a pixel signal
output from each of the first, third, fifth, and seventh subpixels
SPX11, SPX13, SPX15, and SPX17, as one signal to a signal processor
(for example, 130 of FIG. 2) or the outside of the image sensor.
Subsequently, the buffer 155 may output data, corresponding to a
pixel signal output from each of the second, fourth, sixth, and
eighth subpixels SPX12, SPX14, SPX16, and SPX18, as one signal to
the signal processor 130 or the outside of the image sensor.
[0102] From the foregoing, those skilled in the art will recognize
that an image sensor according to embodiments of the inventive
concept may include a subpixel array (e.g., the first subpixel
array 100_1e of FIG. 6A) and may perform an AF function according
to pixel units in the high resolution mode, or perform the AF
function according to pixel group units in the low resolution
mode.
[0103] In other embodiments of the inventive concept additionally
capable of operating in medium resolution mode, image sensor
including the first subpixel array 100_1e may perform the analog
pixel binning operation or the digital pixel binning operation.
Therefore, the image sensor including the first subpixel array
100_1e may perform an AF function according to pixel units in the
high resolution mode, perform the AF function according to pixel
group units in the low resolution mode. In this manner, image
sensors according to embodiments of the inventive concept may
effectively operate in the high resolution mode, the low resolution
mode, and the medium resolution mode to properly meet the needs of
the illumination environment.
[0104] Referring to FIG. 6B, a first subpixel array 100_1f includes
first to fourth pixel groups PG1f to PG4f, wherein each of the
first to fourth pixel groups PG1f to PG4f includes a plurality of
horizontal pixels PX_X. Adjacently disposed (in the X direction)
horizontal pixels PX_X among the plurality of horizontal pixels
PX_X may configured in a shared pixel structure SHPX2X in order to
share a single floating diffusion region. That is, the shared pixel
structure SHPX2X of FIG. 6B is a 4-shared structure including four
subpixels that share a single floating diffusion region.
[0105] An image sensor including the first subpixel array 100_1f
may perform an AF function according to pixel units in the high
resolution mode, and may perform the AF function according to pixel
groups units in conjunction with the first to fourth pixel groups
PG1f to PG4f in the low resolution mode. For example, in the high
resolution mode, the first subpixel array 100_1f may output a pixel
signal VOUT according to the above-described RSSRSSRSSRSS readout
method. Alternatively, the first subpixel array 100_1f may output
the pixel signal VOUT according to the above-described
RSRSRSRSRSRSRSRS readout method.
[0106] Alternatively, in the high resolution mode, the first
subpixel array 100_1f may accumulate all photoelectric charge,
generated by four different photodiodes, into one floating
diffusion region. For example, the first subpixel array 100_1f may
output a reset voltage as a pixel signal VOUT, and then, may output
a pixel signal VOUT based on a first subpixel SPX11, output a pixel
signal VOUT based on the first subpixel SPX11 and a second subpixel
SPX12, output a pixel signal VOUT based on the first to third
subpixels SPX11 to SPX13, and output a pixel signal VOUT based on
the first to fourth subpixels SPX11 to SPX14. Such a readout method
may be a
reset-signal-signal-signal-signal-reset-signal-signal-signal-signal
(RSSSSRSSSS) readout method.
[0107] Alternatively, for example, in the high resolution mode, the
first subpixel array 100_1f may output the reset voltage as the
pixel signal VOUT, and then, may output the pixel signal VOUT based
on the first subpixel SPX11, output the pixel signal VOUT based on
the first subpixel SPX11 and the second subpixel SPX12, and output
the pixel signal VOUT based on the first to fourth subpixels SPX11
to SPX14. That is, in the high resolution mode, the first subpixel
array 100_1f may simultaneously accumulate photoelectric charge,
generated by photodiodes of the third and fourth subpixels SPX13
and SPX14, into one floating diffusion region. Such a readout
method may be a
reset-signal-signal-signal-reset-signal-signal-signal (RSSSRSSS)
readout method. In this case, the third and fourth subpixels SPX13
and SPX14 may not be used for the AF function, but a total readout
speed of the first subpixel array 100_1f may increase.
[0108] On the other hand, an image sensor including the first
subpixel array 100_1f may perform an analog pixel binning operation
in the low resolution mode. For example, the first subpixel array
100_1f may output a pixel signal VOUT based on first, third, fifth,
and seventh subpixels SPX11, SPX13, SPX15, and SPX17 to a first
column output line CLO_0, and then, may output a pixel signal VOUT
based on first to eighth subpixels SPX11 to SPX18 to the first
column output line CLO_0. Alternatively, for example, the first
subpixel array 100_1f may output the pixel signal VOUT based on the
first, third, fifth, and seventh subpixels SPX11, SPX13, SPX15, and
SPX17 to the first column output line CLO_0, subsequently output a
reset voltage as a pixel signal VOUT to the first column output
line CLO_0 again, and subsequently output a pixel signal VOUT based
on the second, fourth, sixth, and eighth subpixels SPX12, SPX14,
SPX16, and SPX18 to the first column output line CLO_0.
[0109] On the other hand, the first subpixel array 100_1f may
perform a digital pixel binning operation in the low resolution
mode. For example, the first subpixel array 100_1f may output a
pixel signal VOUT based on the first and third subpixels SPX11 and
SPX13 and a pixel signal VOUT based on the fifth and seventh
subpixels SPX15 and SPX17 to different column output lines, and
each of the pixel signals VOUT may be converted into a digital
signal by a CDS (for example, 151 of FIG. 2) and an ADC (for
example, 153 of FIG. 2) and may be stored in a buffer (for example,
155 of FIG. 2). The buffer 155 may output data, corresponding to a
pixel signal output from each of the first, third, fifth, and
seventh subpixels SPX11, SPX13, SPX15, and SPX17, as one signal to
a signal processor (for example, 130 of FIG. 2) or the outside of
the image sensor. Subsequently, the buffer 155 may output data,
corresponding to a pixel signal output from each of the second,
fourth, sixth, and eighth subpixels SPX12, SPX14, SPX16, and SPX18,
as one signal to the signal processor 130 or the outside of the
image sensor. Therefore, an image sensor including the first
subpixel array 100_1f may perform an AF function according to pixel
units in the high resolution mode, and may perform the AF function
in pixel group units in the low resolution mode. A first subpixel
array 100_1g may include first to fourth pixel groups PG1g to PG4g,
and each of the first to fourth pixel groups PG1g to PG4g may
include a plurality of horizontal pixels PX_X. Adjacently disposed
(in the Y direction) horizontal pixels PX_X among the plurality of
horizontal pixels PX_X may configured in a shared pixel structure
SHPX2Y which shares a single floating diffusion region. That is,
the shared pixel structure SHPX2Y may be a 4-shared structure
including four subpixels, and four subpixels each time may
configured in the shared pixel structure SHPX2Y, which shares a
floating diffusion region. In each of the high resolution mode and
the low resolution mode, the description of the operation of the
first subpixel array 100_1f described above may be similarly
applied to an operation of the first subpixel array 100_1g.
[0110] Referring to FIG. 6C, a first subpixel array 100_1h includes
first to fourth pixel groups PG1h to PG4h, wherein each of the
first to fourth pixel groups PG1h to PG4h includes a plurality of
horizontal pixels PX_X, wherein the horizontal pixels PX_X included
in a particular same group are configured in a shared pixel
structure SHPX3 which shares a floating diffusion region. That is,
the shared pixel structure SHPX3 may be an 8-shared structure
including eight subpixels, and eight subpixels each time may
configure the shared pixel structure SHPX3, which shares a floating
diffusion region. Therefore, subpixels included in different pixel
groups may not share a floating diffusion region. An operation of
the first subpixel array 100_1h in a high resolution mode and an
operation of the first subpixel array 100_1h in a low resolution
mode will be described below with reference FIG. 9 to FIG. 11.
[0111] Referring to FIG. 6D, a first subpixel array 100_1i include
first to fourth pixel groups PG1i to PG4i, wherein each of the
first to fourth pixel groups PG1i to PG4i includes a plurality of
horizontal pixels PX_X. Adjacently disposed (in the X direction)
horizontal pixels PX_X may be configured in a shared pixel
structure SHPX4X which shares a single floating diffusion region.
That is, the shared pixel structure SHPX4X may be a 16-shared
structure including sixteen subpixels, and sixteen subpixels each
time may configure the shared pixel structure SHPX4X, which shares
a floating diffusion region.
[0112] For example, first to eighth subpixels SPX11 to SPX18 of the
first pixel group PG1i and first to eighth subpixels SPX21 to SPX28
of the second pixel group PG2i may configure one shared pixel
structure SHPX4X, which shares a floating diffusion region, and
first to eighth subpixels SPX31 to SPX38 of the third pixel group
PG3i and first to eighth subpixels SPX41 to SPX48 of the fourth
pixel group PG4i may configure one shared pixel structure SHPX4X,
which shares a floating diffusion region. Therefore, subpixels
included in different pixel groups may share a floating diffusion
region.
[0113] A first subpixel array 100_1j includes first to fourth pixel
groups PG1j to PG4j, wherein each of the first to fourth pixel
groups PG_1j to PG4j includes a plurality of horizontal pixels
PX_X. Adjacently disposed (in the Y direction) horizontal pixels
PX_X may be configured in a shared pixel structure SHPX4Y which
shares a single floating diffusion region. That is, the shared
pixel structure SHPX4Y may be a 16-shared structure including
sixteen subpixels, and sixteen subpixels each time may configure
the shared pixel structure SHPX4Y, which shares a floating
diffusion region.
[0114] For example, first to eighth subpixels SPX11 to SPX18 of the
first pixel group PG1j and first to eighth subpixels SPX31 to SPX38
of the third pixel group PG3j may configure one shared pixel
structure SHPX4Y, which shares a floating diffusion region, and
first to eighth subpixels SPX21 to SPX28 of the second pixel group
PG2j and first to eighth subpixels SPX41 to SPX48 of the fourth
pixel group PG4j may configure one shared pixel structure SHPX4Y,
which shares a floating diffusion region. Therefore, subpixels
included in different pixel groups may share a floating diffusion
region.
[0115] The description of the first subpixel array 100_1h of FIG.
6C in the high resolution mode may be similarly applied to an
operation of each of the first subpixel arrays 100_1i and 100_1j in
the high resolution mode, and the description of the first subpixel
array 100_1h of FIG. 6C in the low resolution mode may be similarly
applied to an operation of each of the first subpixel arrays 100_1i
and 100_1j in the low resolution mode.
[0116] Referring to FIG. 6E, a first subpixel array 100_1k includes
first to fourth pixel groups PG1k to PG4k, wherein each of the
first to fourth pixel groups PG1k to PG4k includes a plurality of
horizontal pixels PX_X. The horizontal pixels PX_X included in the
first to fourth pixel groups PG1k to PG4k may configured in a
shared pixel structure SHPXS which shares a single floating
diffusion region. That is, the shared pixel structure SHPXS may be
a 32-shared structure including thirty-two subpixels, and
thirty-two subpixels each time may configure the shared pixel
structure SHPXS, which shares a floating diffusion region. The
description of the first subpixel array 100_1h of FIG. 6C in the
high resolution mode may be similarly applied to an operation of
the first subpixel array 100_1k in the high resolution mode, and
the description of the first subpixel array 100_1h of FIG. 6C in
the low resolution mode may be similarly applied to an operation of
the first subpixel array 100_1k in the low resolution mode.
[0117] In the illustrated embodiments of FIGS. 6A, 6B, 6C, 6D and
6E, the shared pixel structures SHPX1, SHPX2, SHPX3, SHPX4 and
SHPXS respectively provided in the first subpixel arrays 110_1e,
110_1f, 110_1g, 110_1h, 110_1i, 110_1j and 110_1k have been
described above in some particular detail. However, image sensors
according to embodiments of the inventive concept are not limited
thereto, and the structure of various subpixel arrays may be
variously implemented.
[0118] FIG. 7 is a circuit diagram further illustrating in one
embodiment an arrangement of subpixels sharing a floating diffusion
region. In FIG. 7, a shared pixel structure provides a dual
conversion gain (DCG) function. The shared pixel structure of FIG.
7 assumes four photodiodes sharing a first floating diffusion
region HCG_FD_A, and four photodiodes sharing a second floating
diffusion region HCG_FD_B.
[0119] Referring to FIG. 7, a shared pixel structure SHPX' includes
first to eighth photodiodes PD11 to PD18, first to eighth
transmission transistors TX11 to TX18, first and second selection
transistors SX1 and SX2, first and second drive transistors SF1 and
SF2, and first to fourth reset transistors RX11, RX21, RX12, and
RX22.
[0120] The first to fourth transmission transistors TX11 to TX14
may respectively connect the first to fourth photodiodes PD11 to
PD14 to the first floating diffusion region HCG_FD_A in response to
first to fourth transmission control signals TS11 to TS14
corresponding thereto. The fifth to eighth transmission transistors
TX15 to TX18 may respectively connect the fifth to eighth
photodiodes PD15 to PD18 to the second floating diffusion region
HCG_FD_B in response to fifth to eighth transmission control
signals TS15 to TS18 corresponding thereto. For example, subpixels
including the first to fourth photodiodes PD11 to PD14 may share
the first floating diffusion region HCG_FD_A, and subpixels
including the fifth to eighth photodiodes PD15 to PD18 may share
the second floating diffusion region HCG_FD_B.
[0121] The first reset transistor RX11 and the second reset
transistor RX21 may periodically reset photoelectric charge
accumulated into the first floating diffusion region HCG_FD_A in
response to the first reset control signal RS11 and the second
reset control signal RS21. A source electrode of the first reset
transistor RX11 may be connected to the first floating diffusion
region HCG_FD_A, and a drain electrode thereof may be connected to
the second reset transistor RX21 and a third floating diffusion
region LCG_FD. A source electrode of the second reset transistor
RX21 may be connected to the first reset transistor RX11 and the
third floating diffusion region LCG_FD, and a drain electrode
thereof may be connected to a source voltage VPIX.
[0122] The third reset transistor RX12 and the fourth reset
transistor RX22 may periodically reset photoelectric charge
accumulated into the second floating diffusion region HCG_FD_B in
response to the third reset control signal RS12 and the fourth
reset control signal RS22. A source electrode of the third reset
transistor RX12 may be connected to the second floating diffusion
region HCG_FD_B, and a drain electrode thereof may be connected to
the fourth reset transistor RX22 and the third floating diffusion
region LCG_FD. A source electrode of the fourth reset transistor
RX22 may be connected to the third reset transistor RX12 and the
third floating diffusion region LCG_FD, and a drain electrode
thereof may be connected to the source voltage VPIX.
[0123] When the first reset transistor RX11 is turned ON, the first
floating diffusion region HCG_FD_A may be connected to the third
floating diffusion region LCG_FD. Moreover, when the third reset
transistor RX12 is turned ON, the second floating diffusion region
HCG_FD_B may be connected to the third floating diffusion region
LCG_FD. Therefore, when all of the first and third reset
transistors RX11 and RX12 are turned ON, the first floating
diffusion region HCG_FD_A, the second floating diffusion region
HCG_FD_B, and the third floating diffusion region LCG_FD may be
connected to one another. Therefore, the shared pixel structure of
the image sensor according to an embodiment may be changed from the
shared pixel structures SHPX2X and SHPX2Y of the 4-shared structure
of FIG. 6B to the shared pixel structure SHPX3 of the 8-shared
structure of FIG. 6C.
[0124] The first selection transistor SX1 and the second selection
transistor SX2 may output a pixel signal VOUT to a CDS (for
example, 151 of FIG. 2) through a column output line in response to
a first selection signal SELS1 and a second selection signal
SELS2.
[0125] In an image sensor according to embodiments of the inventive
concept, as the capacitance of a floating diffusion region
decreases/increases, a conversion gain will increase/decrease
accordingly. Thus, as the capacitance of a floating diffusion
region increases, relatively more photoelectric charge is
accumulated in the floating diffusion region. Thus result decreases
the number of reset operations that must be performed and therefore
increases overall operating speed. Therefore, depending on the
case, a pixel array may operate in the 4-shared structure in a high
conversion gain (HCG) mode and may operate in the 8-shared
structure in a low conversion gain (LCG) mode, thereby supporting a
dual conversion gain (DCG) functions.
[0126] FIGS. 8, 9, 10 and 11 are respective timing diagrams further
illustrating an operation of an image sensor according to
embodiments of the inventive concept. In the timing diagrams, for
convenience of description, the image sensor described with
reference to the first subpixel array 100_1h including the shared
pixel structure SHPX3 illustrated in FIG. 6C is assumed.
[0127] In one embodiment, operation of an image sensor is described
with reference to FIGS. 8 and 9. A plurality of horizontal pixels
PX_X included in the first subpixel array 100_1h providing a pixel
signal for an AF function in the high resolution mode is further
assumed. In another embodiment, operation of an image sensor is
described with reference to FIG. 10. Here again, a plurality of
horizontal pixels PX_X included in the first subpixel array 100_1h
providing a pixel signal for an AF function in the high resolution
mode is assumed. In still another embodiment, operation of an image
sensor described below with reference to FIG. 11 may be an
embodiment where a pixel group outputs a pixel signal for an AF
function in the low resolution mode.
[0128] Referring collectively to FIGS. 5, 6C, and 8, in the first
subpixel SPX11, photoelectric charge generated by the first
photodiode PD11 is accumulated in the floating diffusion region FD1
in response to a switching operation of the first transmission
transistor TX11 controlled by the first transmission control signal
TS11. In the second subpixel SPX12, photoelectric charge generated
by the second photodiode PD12 is accumulated in the floating
diffusion region FD1 in response to a switching operation of the
second transmission transistor TX12 controlled by the second
transmission control signal TS12. In the seventh subpixel SPX17,
photoelectric charge generated by a seventh photodiode is
accumulated in the floating diffusion region FD1 in response to a
switching operation of a seventh transmission transistor controlled
by the seventh transmission control signal TS17, and in the eighth
subpixel SPX18, photoelectric charge generated by an eighth
photodiode is accumulated in the floating diffusion region FD1 in
response to a switching operation of an eighth transmission
transistor controlled by the eighth transmission control signal
TS18.
[0129] The first pixel group PG1h may be reset, and then, first to
eighth transmission transistors of the first to eighth subpixels
SPX11 to SPX18 may be sequentially turned ON. That is, the reset
control signal RS1 may be shifted from a logic high level to a
logic low level, and then, the first to eighth transmission control
signals TS11 to TS18 may be sequentially shifted from a logic low
level to a logic high level.
[0130] A ramp voltage RMP generated by a ramp signal generator
(e.g., ramp signal generator 157 of FIG. 2) may include nine pulses
during a period where the reset control signal RS1 is shifted from
a logic high level to a logic low level and then is shifted to a
logic high level again. Each of the pulses may have a
triangular-wave shape which sequentially decreases and then
increases at a time again. As shown in FIG. 8, the pulse may
progressive increase in amplitude swing with each activation, but
this signaling approach is merely one example.
[0131] Thus, a first pulse R may be a pulse corresponding to a
pixel voltage VOUT when the floating diffusion region FD1 of the
first pixel group PG1h is reset. A reset voltage may be relatively
low in level of a varying signal.
[0132] A second pulse S1 may be a pulse corresponding to a pixel
signal VOUT based on a photoelectric charge generated by the first
photodiode PD11 of the first subpixel SPX11. In the pixel signal
VOUT, voltage drop may be added to the reset voltage, and thus, the
second pulse S1 may be adjusted to dip lower than the first pulse R
and then be restored.
[0133] A third pulse S1S2 may be a pulse corresponding to a pixel
signal VOUT based on photoelectric charge generated by the first
photodiode PD11 of the first subpixel SPX11 and the second
photodiode PD12 of the second subpixel SPX12. A fourth pulse S1 . .
. S7 may be a pulse corresponding to a pixel signal VOUT based on
photoelectric charge generated by first to seventh photodiodes of
the first to seventh subpixels SPX11 to SPX17, and a fifth pulse S1
. . . S8 may be a pulse corresponding to a pixel signal VOUT based
on photoelectric charge generated by first to eighth photodiodes of
the first to eighth subpixels SPX11 to SPX18.
[0134] As described above, a waveform of the ramp voltage RMP may
be derived from the pixel signal VOUT output from the first pixel
group PG1h. That is, the first pixel group PG1h may first output a
reset voltage as a pixel signal VOUT, and then, may output a pixel
signal VOUT based on the first subpixel SPX11, output a pixel
signal VOUT based on the first subpixel SPX11 and the second
subpixel SPX12, output a pixel signal VOUT based on the first to
third subpixels SPX11 to SPX13, output a pixel signal VOUT based on
the first to fourth subpixels SPX11 to SPX14, output a pixel signal
VOUT based on the first to fifth subpixels SPX11 to SPX15, output a
pixel signal VOUT based on the first to sixth subpixels SPX11 to
SPX16, output a pixel signal VOUT based on the first to seventh
subpixels SPX11 to SPX17, and output a pixel signal VOUT based on
the first to eighth subpixels SPX11 to SPX18. Such a readout method
may be a
reset-signal-signal-signal-signal-signal-signal-signal-signal
(RSSSSSSSS) readout method.
[0135] The photoelectric charge generated by the first to eighth
subpixels SPX11 to SPX18 included in the first pixel group PG1h may
be sequentially accumulated in the floating diffusion region FD1,
and pixel signals VOUT based thereon may be sequentially output.
The pixel signals VOUT corresponding to the photoelectric charge
generated by the first to eighth subpixels SPX11 to SPX18 may be
sequentially output after a reset operation is performed on the
first pixel group PG1h once, and thus, the image sensor according
to the present disclosure may perform a high-speed operation.
Therefore, when a high-speed operation is needed like a moving
image mode, the number of reset operations may decrease, and the
photoelectric charge generated by the first to eighth subpixels
SPX11 to SPX18 may be sequentially accumulated in the floating
diffusion region FD1.
[0136] Moreover, the first to eighth transmission transistors of
the first to eighth subpixels SPX11 to SPX18 may be sequentially
turned ON (i.e. the TS11_on to TS18_on as shown in FIG. 8), and the
pixel signals VOUT corresponding to the photoelectric charge
generated by the first to eighth subpixels SPX11 to SPX18 may be
sequentially output, thereby providing the high resolution mode
which allows the AF function to be performed in units of pixels. At
this time, each of the plurality of pixels PX_X included in the
first pixel group PG1h may output a pixel signal VOUT including AF
information.
[0137] Referring collectively to FIGS. 5, 6C, and 9, first to
eighth transmission transistors of the first to eighth subpixels
SPX11 to SPX18 may be sequentially turned ON. That is, the first to
eighth transmission control signals TS11 to TS18 may be
sequentially shifted from a logic low level to a logic high
level.
[0138] A first pulse R1 of a ramp voltage RMP may be a pulse
corresponding to a pixel voltage VOUT of when the floating
diffusion region FD1 of the first pixel group PG1h is reset. A
second pulse S1 may be a pulse corresponding to a pixel signal VOUT
based on a photoelectric charge generated by the first photodiode
PD11 of the first subpixel SPX11. A third pulse S1S2 may be a pulse
corresponding to a pixel signal VOUT based on photoelectric charge
generated by the first photodiode PD11 of the first subpixel SPX11
and the second photodiode PD12 of the second subpixel SPX12.
[0139] A fourth pulse R4 may be a pulse corresponding to a pixel
voltage VOUT of when the floating diffusion region FD1 of the first
pixel group PG1h is reset. A fifth pulse S7 may be a pulse
corresponding to a pixel signal VOUT based on a photoelectric
charge generated by the seventh photodiode of the seventh subpixel
SPX17. A sixth pulse S7S8 may be a pulse corresponding to a pixel
signal VOUT based on photoelectric charge generated by the seventh
photodiode of the seventh subpixel SPX17 and the eighth photodiode
of the eighth subpixel SPX18.
[0140] The first pixel group PG1h may first output a reset voltage
as a pixel signal VOUT, and then, may output a pixel signal VOUT
based on the first subpixel SPX11 and may output a pixel signal
VOUT based on the first subpixel SPX11 and the second subpixel
SPX12, Subsequently, the first pixel group PG1h may first output
the reset voltage as a pixel signal VOUT, and then, may output a
pixel signal VOUT based on the third subpixel SPX13 and may output
a pixel signal VOUT based on the third subpixel SPX13 and the
fourth subpixel SPX14. Subsequently, the first pixel group PG1h may
output the reset voltage as a pixel signal VOUT, and then, may
output a pixel signal VOUT based on the fifth subpixel SPX15 and
may output a pixel signal VOUT based on the fifth subpixel SPX15
and the sixth subpixel SPX16. Subsequently, the first pixel group
PG1h may output the reset voltage as a pixel signal VOUT, and then,
may output a pixel signal VOUT based on the seventh subpixel SPX17
and may output a pixel signal VOUT based on the seventh subpixel
SPX17 and the eighth subpixel SPX18. Such a readout method may be
the RSSRSSRSSRSS readout method described above with reference to
FIG. 6B.
[0141] The photoelectric charge generated by some (e.g., selected
ones) of the first to eighth subpixels SPX11 to SPX18 included in
the first pixel group PG1h is accumulated in the floating diffusion
region FD1, and after the floating diffusion region FD1 is reset,
photoelectric charge generated by some other subpixels is
accumulated in the floating diffusion region FD1 again.
Accordingly, even when a capacitance of the floating diffusion
region FD1 is low, the image sensor according to the present
disclosure may provide the AF function. Moreover, the first to
eighth transmission transistors of the first to eighth subpixels
SPX11 to SPX18 may be sequentially turned ON, and the pixel signals
VOUT corresponding to the photoelectric charge generated by the
first to eighth subpixels SPX11 to SPX18 may be sequentially
output, thereby providing the high resolution mode which allows the
AF function to be performed in units of pixels. At this time, each
of the plurality of pixels PX_X included in the first pixel group
PG1h may output a pixel signal VOUT including AF information.
[0142] Image sensors according to embodiments of the inventive
concept are not limited to the above-described readout method(s).
The process of outputting a pixel signal VOUT based on each of the
first to eighth subpixels SPX11 to SPX18 may use a readout method
(i.e., an RSSSSRSSSS readout method) where a pixel signal VOUT is
output while sequentially accumulating photoelectric charge,
generated by photodiodes of four subpixels, in the floating
diffusion region FD1, and then, a reset operation is repeated.
Alternatively, the process may use a readout method (i.e., an
RSRSRSRSRSRSRSRS readout method) where a pixel signal VOUT based on
one subpixel is output, and then, a reset operation is
repeated.
[0143] Referring collectively to FIGS. 5, 6C, and 10, the first
transmission transistor TX11 of the first subpixel SPX11 and the
second transmission transistor TX12 of the second subpixel SPX12
may be simultaneously turned ON, and the third to eighth
transmission transistors of the third to eighth subpixels SPX13 to
SPX18 may be sequentially turned ON. That is, the first
transmission control signal TS11 and the second transmission
control signal TS12 may be simultaneously shifted from a logic low
level to a logic high level, and the third to eighth transmission
control signals TS13 to TS18 may be sequentially shifted from a
logic low level to a logic high level.
[0144] A first pulse R of a ramp voltage RMP may be a pulse
corresponding to a pixel voltage VOUT of when the floating
diffusion region FD1 of the first pixel group PG1h is reset. A
second pulse S1S2 may be a pulse corresponding to a pixel signal
VOUT based on photoelectric charge generated by the first
photodiode PD11 of the first subpixel SPX11 and the second
photodiode PD12 of the second subpixel SPX12. A third pulse S1 . .
. S7 may be a pulse corresponding to a pixel signal VOUT based on
photoelectric charge generated by the first to seventh photodiodes
of the first to seventh subpixels SPX11 to SPX17, and a fourth
pulse S1 . . . S8 may be a pulse corresponding to a pixel signal
VOUT based on photoelectric charge generated by first to eighth
photodiodes of the first to eighth subpixels SPX11 to SPX18.
[0145] That is, the first pixel group PG1h may first output a reset
voltage as a pixel signal VOUT, and then, may output a pixel signal
VOUT based on the first subpixel SPX11 and the second subpixel
SPX12, output a pixel signal VOUT based on the first to third
subpixels SPX11 to SPX13, output a pixel signal VOUT based on the
first to fourth subpixels SPX11 to SPX14, output a pixel signal
VOUT based on the first to fifth subpixels SPX11 to SPX15, output a
pixel signal VOUT based on the first to sixth subpixels SPX11 to
SPX16, output a pixel signal VOUT based on the first to seventh
subpixels SPX11 to SPX17, and output a pixel signal VOUT based on
the first to eighth subpixels SPX11 to SPX18. Such a readout method
may be a reset-signal-signal-signal-signal-signal-signal-signal
(RSSSSSSS) readout method.
[0146] In performing the AF function, the image sensor according to
the present disclosure may not use some (i.e., non-selected ones)
of the plurality of horizontal pixels PX_X included in the first
pixel group PG1h. For example, since the first and second subpixels
SPX11 and SPX12 simultaneously accumulate photoelectric charge in
the floating diffusion region FD1, the first and second subpixels
SPX11 and SPX12 may not be used for the AF function, and the third
to eighth subpixels SPX13 to SPX18 may be used for the AF
function.
[0147] In FIG. 10, a case where only the first and second subpixels
SPX11 and SPX12 are not used for the AF function has been described
above, but embodiments of the inventive concept are not limited
thereto. The first and second subpixels SPX11 and SPX12 may
simultaneously accumulate photoelectric charge in the floating
diffusion region FD1, and then, the third and fourth subpixels
SPX13 and SPX14 may simultaneously accumulate photoelectric charge
in the floating diffusion region FD1, whereby the first to fourth
subpixels SPX11 to SPX14 may not be used for the AF function. Such
a readout method may be a
reset-signal-signal-signal-signal-signal-signal (RSSSSSS) readout
method. At this time, the fourth to eighth subpixels SPX14 to SPX18
may sequentially accumulate photoelectric charge in the floating
diffusion region FD1, and thus, may be used for the AF
function.
[0148] Alternatively, the first and second subpixels SPX11 and
SPX12 may simultaneously accumulate photoelectric charge in the
floating diffusion region FD1, the third and fourth subpixels SPX13
and SPX14 may simultaneously accumulate photoelectric charge in the
floating diffusion region FD1 subsequently, and the fifth and sixth
subpixels SPX15 and SPX16 may simultaneously accumulate
photoelectric charge in the floating diffusion region FD1
subsequently, whereby the first to sixth subpixels SPX11 to SPX16
may not be used for the AF function. Such a readout method may be a
reset-signal-signal-signal-signal-signal (RSSSSS) readout method.
At this time, the seventh and eighth subpixels SPX17 and SPX18 may
sequentially accumulate photoelectric charge in the floating
diffusion region FD1, and thus, may be used for the AF
function.
[0149] An image sensor according to certain embodiments of the
inventive concept may operate such that subpixels of the same pixel
among the first to eighth subpixels SPX11 to SPX18 accumulate
photoelectric charge in the floating diffusion region FD1
simultaneously, thereby facilitating high-speed operation. However,
in other embodiments, an image sensor may perform a method of
accumulating photoelectric charge generated by photodiodes of four
(4) subpixels in the floating diffusion region FD1, and repeating a
reset operation. For example, such an image sensor may perform a
readout method (e.g., an RSSSRSSS readout method) of repeating
twice a method of primarily and simultaneously turning ON two
transmission transistors of a single pixel, and then, sequentially
turning ON the other transmission transistors one by one.
[0150] From the foregoing, those skilled in the art will recognize
that a readout method for use with an image sensor according to
embodiments of the inventive concept may be variously
implemented.
[0151] Referring collectively to FIGS. 5, 6C, and 11, transmission
transistors of subpixels having the same phase may be
simultaneously turned ON. For example, first, third, fifth, and
seventh transmission transistors of the first, third, fifth, and
seventh subpixels SPX11, SPX13, SPX15, and SPX17 phase may be
simultaneously turned ON, and then, second, fourth, sixth, and
eighth transmission transistors of second, fourth, sixth, and
eighth subpixels SPX12, SPX14, SPX16, and SPX18 may be
simultaneously turned ON. That is, the first, third, fifth, and
seventh transmission control signals TS11, TS13, TS15, and TS17 may
be simultaneously shifted from a logic low level to a logic high
level, and the second, fourth, sixth, and eighth transmission
control signals TS12, TS14, TS16, and TS18 may be simultaneously
shifted from a logic low level to a logic high level.
[0152] A first pulse R of a ramp voltage RMP may be a pulse
corresponding to a pixel voltage VOUT of when the floating
diffusion region FD1 of the first pixel group PG1h is reset. A
second pulse S1S3S5S7 may be a pulse corresponding to a pixel
signal VOUT based on photoelectric charge generated by first,
third, fifth, and seventh photodiodes of the first, third, fifth,
and seventh subpixels SPX11, SPX13, SPX15, and SPX17. A third pulse
S1 . . . S8 may be a pulse corresponding to a pixel signal VOUT
based on photoelectric charge generated by the first to eighth
photodiodes of the first to eighth subpixels SPX11 to SPX18. That
is, the first pixel group PG1h may first output a reset voltage as
a pixel signal VOUT, and then, may output a pixel signal VOUT based
on the first, third, fifth, and seventh subpixels SPX11, SPX13,
SPX15, and SPX17 and may output a pixel signal VOUT based on the
first to eighth subpixels SPX11 to SPX18. Such a readout method may
be a reset-signal-signal (RSS) readout method.
[0153] An image sensor according to embodiments of the inventive
concept may perform an AF function in pixel group units in the low
resolution mode. That is, the AF function may be performed by
comparing a pixel signal VOUT based on photoelectric charge
generated by the first, third, fifth, and seventh photodiodes with
a pixel signal VOUT based on photoelectric charge generated by the
second, fourth, sixth, and eighth photodiodes. The amount of
photoelectric charge generated by one photodiode may be reduced in
a low illumination environment, and thus, the image sensor may
accumulate all photoelectric charge generated by a plurality of
photodiodes in order to properly perform the AF function.
[0154] However, the image sensor according to the present
disclosure is not limited to the embodiment illustrated in FIG. 11.
For example, the first pixel group PG1h may output a pixel signal
VOUT based on the first, third, fifth, and seventh subpixels SPX11,
SPX13, SPX15, and SPX17 and may be reset, and then, may output a
pixel signal VOUT based on the second, fourth, sixth, and eighth
subpixels SPX12, SPX14, SPX16, and SPX18 in a
reset-signal-reset-signal (RSRS) readout method. In a
reset-signal-reset-signal-reset-signal-reset-signal (RSRSRSRS)
readout method, the first pixel group PG1h may first output a reset
voltage as a pixel signal VOUT, and then, may output a pixel signal
VOUT based on the first and fifth subpixels SPX11 and SPX15 and may
be reset, may output a pixel signal VOUT based on the second and
sixth subpixels SPX12 and SPX16 subsequently and may be reset
again, may output a pixel signal VOUT based on the third and
seventh subpixels SPX13 and SPX17 subsequently and may be reset
again, and may output a pixel signal VOUT based on the fourth and
eighth subpixels SPX14 and SPX18 subsequently. In a
reset-signal-signal-reset-signal-signal (RSSRSS) readout method,
the first pixel group PG1h may first output a reset voltage as a
pixel signal VOUT, and then, may output a pixel signal VOUT based
on the first and fifth subpixels SPX11 and SPX15, may output a
pixel signal VOUT based on the first, second, fifth, and sixth
subpixels SPX11, SPX12, SPX15, and SPX16 subsequently and may be
reset, may output a pixel signal VOUT based on the third and
seventh subpixels SPX13 and SPX17, and may output a pixel signal
VOUT based on the third, fourth, seventh, and eighth subpixels
SPX13, SPX14, SPX17, and SPX18. The image sensor according to the
present disclosure is not limited to operating based on the
above-described operating methods (for example, the
reset-signal-signal-reset-signal-signal (RSSRSS) readout method.
Various combinations of the above-described operating methods may
be applied to the image sensor according to the present
disclosure.
[0155] FIG. 12 is yet another diagram illustrating a pixel array of
an image sensor according to certain embodiments of the inventive
concept.
[0156] Referring to FIGS. 3A and 12, a first subpixel array 110_1d
includes a plurality of horizontal pixels PX_X arranged in a row
direction (i.e., a first direction X) and in a column direction
(i.e., a second direction Y). Each of the horizontal pixels PX_X is
further assumed to be operationally configured with a micro-lens
ML.
[0157] In the illustrated embodiment, each of first to fourth pixel
groups PG1d to PG4d includes nine (9) horizontal pixels PX_X,
wherein each one of the horizontal pixels PX_X include two (2)
subpixels adjacently disposed in the first direction X. For
example, each of the first to fourth pixel groups PG1d to PG4d may
include eighteen subpixels arranged in three rows, six columns. For
example, the first pixel group PG1d may include first to eighteen
subpixels SPX11 to SPX118, the second pixel group PG2d may include
first to eighteen subpixels SPX21 to SPX218, the third pixel group
PG3d may include first to eighteen subpixels SPX31 to SPX318, and
the fourth pixel group PG4d may include first to eighteen subpixels
SPX41 to SPX418.
[0158] The first subpixel array 110_1d may variously include one or
more color filter(s) as previously described. Here, the respective
horizontal pixels PX_X of each one first to fourth pixel groups
PG1d to PG4d are associated with a selected color filter.
[0159] In an embodiment, the first subpixel array 110_1d may be
configured according to a shared pixel structure wherein two
subpixels for each of the horizontal pixels PX_X share a floating
diffusion region. Thus, the first subpixel array 110_1d may include
nine (9) floating diffusion regions for each pixel group PG1d,
PG2d, PG3d and PG4d.
[0160] In one approach, the first subpixel array 110_1d may be
configured in a shared pixel structure wherein horizontal pixels
PX_X disposed in the same row of a pixel group share one floating
diffusion region. Alternatively, the first subpixel array 110_1d
may be configured in a shared pixel structure wherein horizontal
pixels PX_X disposed in the same column of a pixel group share one
floating diffusion region. In this manner, three (3) floating
diffusion regions may be provided in each pixel group.
[0161] In another approach, horizontal pixels PX_X included one or
more pixel group(s) may share a floating diffusion region. For
example, the horizontal pixels PX_X included in different pixel
groups may share different floating diffusion regions.
Alternatively, horizontal pixels PX_X included in different pixel
groups adjacent to each other in a row direction (i.e., the first
direction X) may share different floating diffusion regions.
Alternatively, for example, horizontal pixels PX_X included in
different pixel groups adjacent to each other in a column direction
(i.e., the second direction Y) may share different floating
diffusion regions. Alternatively, for example, pixels PX_X included
in the first to fourth pixel groups PG1d to PG4d may share
different floating diffusion regions.
[0162] In an embodiment, an image sensor including the first
subpixel array 110_1d may perform an AF function in pixel units
while operating in a first mode (i.e., the high resolution mode),
but perform the AF function in pixel group units while operating in
a second mode (i.e., the low resolution mode). For example,
resolution associated with the low resolution mode may be less than
or equal to about 1/9 times the resolution associated with a high
resolution mode.
[0163] As previously noted, image sensors according to embodiments
of the inventive concept may effectively provide accurate AF
function capabilities across a range of illumination environments
using multiple resolution modes. Specific examples of high, low and
medium resolution modes have been described above, but embodiments
of the inventive concept may use any reasonable number of
resolution modes having variously defined relationships. For
example, resolution associated with a medium resolution mode may
range from between 1/9 times the resolution associated with a high
resolution mode to 1/3 times the resolution associated with the
high resolution mode.
[0164] Several of the foregoing embodiments have assumed that use
of four (4) pixel groups. However, embodiments of the inventive
concept are not limited thereto. For example the horizontal pixels
PX_X and/or vertical pixels PX_Y of a subpixel array may be
functionally divided into 2, 4, 8, 16 or 32 pixel groups.
[0165] While the inventive concept has been particularly shown and
described with reference to embodiments thereof, it will be
understood that various changes in form and details may be made
therein without departing from the spirit and scope of the
following claims.
* * * * *